Flow-forming machine and forming method for producing a wheel

ABSTRACT

The invention relates to a flow-forming machine and a forming method for producing a wheel having a rim from a workpiece, with a spinning mandrel, the outside of which is configured for forming the rim, a counter-mandrel, wherein the workpiece is clamped on the spinning mandrel or the counter-mandrel, a rotary drive and at least one compression roller, which can be advanced against the workpiece for forming the rim. According to the invention, it is provided that the spinning mandrel has a sleeve-like perimeter element, which can be displaced axially during forming. A controller is provided, by means of which, while the rim is being formed, the at least one compression roller and the perimeter element of the spinning mandrel can be displaced axially relative to the workpiece in a coordinated manner.

The invention relates to a flow-forming machine for producing a wheel, in particular a vehicle wheel, having a rim, from a workpiece, with a spinning mandrel, the outside of which is configured for forming the rim, a counter-mandrel, which can be displaced axially relative to the spinning mandrel, wherein the workpiece is axially clamped on the spinning mandrel and/or the counter-mandrel, a rotary drive for the rotational driving of spinning mandrel and counter-mandrel with the clamped workpiece, and at least one compression roller, which can be advanced against the workpiece axially and radially for forming the rim, according to the preamble of claim 1.

The invention furthermore relates to a forming method for producing a wheel, in particular a vehicle wheel, with a rim, from a workpiece, in which the workpiece is clamped on a spinning mandrel, the outside of which is configured for forming the rim, and/or a counter-mandrel, the clamped workpiece is set in rotation by a rotary drive and at least one compression roller is advanced against the rotating workpiece axially and radially, wherein the rim is formed, according to the preamble of claim 7.

Flow-forming machines and forming methods of this type for producing a wheel, in particular vehicle wheels, have been known for a long time. For instance, a generic method for producing a vehicle wheel from a disc-shaped blank can be taken from DE 196 15 675 A1. The workpiece here is clamped on a spinning mandrel in a flow-forming machine, the external perimeter of said spinning mandrel corresponding to an internal contour of the rim that is to be formed. By means of at least one compression roller, a workpiece region is shaped chipless on the spinning mandrel, forming the rim well and the lateral rim flanges.

In the vehicle wheel industry it is often necessary to offer a model of a vehicle wheel with different widths of the rim. For instance, many vehicles require a greater wheel width on the driven rear axle than on the front axle. Furthermore, it is customary that vehicles of one model from a manufacturer are fitted with vehicle wheels of different wheel widths, depending on the engine power.

To produce vehicle wheels with different rim widths, it is necessary to provide different spinning mandrels. This means that either multiple flow-forming machines with different spinning mandrels are needed, which is very costly; or alternatively, a flow-forming machine can be retooled by replacing the spinning mandrel. However, this procedure is time-consuming and therefore costly.

From WO 2005/065049 A2, a method for producing a vehicle wheel with a drop-center rim is known. A drop-center rim has a radial indent in a center region. For flow forming a drop-center rim of this type, a multi-part spinning mandrel is disclosed, which has to be dismantled after the forming step.

JP S60-158933 A discloses a device for flow forming with an external forming roller and a two-part internal forming roller. The internal forming roller here has a static external contour matching the internal contour of the workpiece.

JP S58-202927 A discloses a device for forming a cylindrical workpiece by advancing an external forming roller, wherein a cylindrical preform is secured on an internal tool with a first and a second tool half.

CN 101 934 326 B discloses a device for forming a cylindrical hollow body by means of an external forming roller and a two-part internal forming tool. The internal contour of the cylindrical workpiece that can be produced corresponds here to the external contour of the internal tool. The internal tool is formed in two parts from parts that can be removed from the cylinder from two opposite sides.

From US 2003/145466 A1 a method for producing wheel rims can be taken, wherein a hollow cylindrical body is provided between two internal forming tools that can be advanced axially, a first shape is introduced into the cylindrical preform by means of a first external forming tool and a second contour is introduced into the workpiece by means of a second external forming roller. The internal contour of the workpiece here corresponds to the external contour of the internal tool.

The invention is based on the object of providing a flow-forming machine and a forming method for producing a wheel, by means of which wheels with different dimensions and shapes can be produced particularly efficiently.

The object is achieved on the one hand by a flow-forming machine having the features of claim 1 and on the other hand by a forming method having the features of claim 7. Preferred embodiments of the invention are specified in the respective dependent claims.

The flow-forming machine according to the invention is characterized in that the spinning mandrel has a sleeve-like perimeter element which can be displaced axially during forming, and that a controller is provided by means of which, while the rim is being shaped, the at least one compression roller and the perimeter element of the spinning mandrel can be moved axially relative to the workpiece in a coordinated manner.

A basic concept of the invention lies in providing a variable spinning mandrel for the forming or flow forming of the rim of a wheel, said spinning mandrel being adjusted or displaced during the forming. Using such a variable, adjustable spinning mandrel, various shapes and dimensions of a drum-like rim can be formed during wheel production. The spinning mandrel here preferably has a disc-shaped front element and a sleeve-like perimeter element, which can be axially adjusted during forming. In this way, the perimeter element can be displaced together with the externally abutting compression roller, for instance, in the same axial direction so that virtually any length of the rim can be fashioned. In the event of dimensional changes to the rim, therefore, a time-consuming and costly retooling of the flow-forming machine is no longer necessary. The adjustment of the sleeve-like perimeter element and the at least one compression roller takes place by means of an electronic controller. The workpiece can be disc-shaped, in which case a radial hub is already pre-formed. Alternatively, the workpiece can be ring-shaped, in which case a hub is attached after the rim has been formed.

A preferred embodiment of the invention consists in the fact that the sleeve-like perimeter element is configured in a conical shape, at least in part, with the perimeter element tapering towards the free end. In the case of a conical configuration of the perimeter element, therefore, various internal diameters are thus available for the internal support of the externally engaging compression roller. Thus, an internal contour of the rim well of the rim can be created with a very wide variety of shapes, wherein even undercut regions, as provided for instance in a drop-center rim, can be formed straightforwardly. In this case, the conical perimeter element is displaced in both directions along the axis of rotation during forming. An external contour of the perimeter element in this case is largely independent of the internal contour of the rim to be formed. The cone only has to extend over the largest and smallest diameters that occur in the internal contour of the rim.

According to a development of the invention, it is advantageous that a forming region is arranged on a region of the perimeter element, which is configured for forming a rim flange on the rim. The forming region in this case has a curved contour so that, as a result, an internal region of the rim flange to be formed is predefined. For wheels with different lengths of the rim well, the shape of the rim flange in the marginal region of the rim often remains unchanged.

In particular for producing a drop-center rim, according to an embodiment of the invention it is preferred that, for forming an axial undercut region in the rim, the controller is configured for the relative axial displacement of the at least one compression roller and the forming element, such that the at least one compression roller initially engages on a first diameter region of the conical perimeter element, next engages on a second diameter region of the perimeter element, which is smaller than the first diameter region, and then engages on a third diameter region of the perimeter element, which is larger than the second diameter region. As a result of an appropriate axial adjustment of the conical perimeter element, for fashioning a central region of the drop-center rim a smaller diameter region can be provided so as to correspond to the compression roller. For the forming of the two side regions, the conical perimeter element is adjusted such that larger diameter regions are opposite each other in the radial direction of the engaging compression roller in each case, so that in this way, overall, an axial undercut region for a drop-center rim can be produced in a central region of the rim.

According to a development of the flow-forming machine according to the invention, it is advantageous that the spinning mandrel has a main support on which the perimeter element is mounted in an axially slideable manner and that on a free front side of the main support a front element is arranged, wherein a radial hub can be clamped axially between the spinning mandrel with the front element and the counter-mandrel. This also allows simple replacement of the sleeve-like perimeter element, should this become necessary for maintenance work or in the event of changes of diameter or design of the wheel to be produced.

In principle, an axial sliding of the perimeter element can take place in any desired manner. It is particularly preferred according to an embodiment variant of the invention that, for the axial sliding of the perimeter element, at least one adjusting element, in particular an adjusting cylinder or a spindle drive, is provided on the main support. Adjusting cylinders, which can be operated hydraulically or pneumatically, represent a typical actuator on conventional flow-forming machines. It is also possible to convert an ejector that may be present with an axial adjusting motion for sliding the perimeter element. Alternatively, a spindle drive, i.e. a rotary drive, can be used, in which the rotary motion is converted to an axial motion by means of an appropriate spindle arrangement.

To increase the variety of shapes, it is provided according to a development of the invention that the front element is fitted on the main support in such a way that it can be replaced. The front element can be provided so as to correspond with the counter-mandrel for the axial clamping of the workpiece in the radially extending disc or hub region. Depending on the design of the hub region, which is pre-formed for instance by casting or forging, the front element and the counter-mandrel are configured accordingly. In the case of appropriate changes of shape, however, the front element can also a corresponding front plate on the counter-mandrel, for instance by releasing screwed joints, easily released and replaced by a new element. For clamping a ring-shaped and/or disc-shaped workpiece, the counter-mandrel can be a chuck for radial clamping.

The method according to the invention is characterized in that the spinning mandrel has a sleeve-like perimeter element, which is displaced axially while the rim is being formed, and that while the rim is being formed the at least one compression roller and the perimeter element of the spinning mandrel are displaced axially relative to the workpiece in a coordinated manner. The method according to the invention can preferably be carried out on the flow-forming machine according to the invention described above. In particular, the advantages described above can be achieved in terms of flexibility and variety of shapes.

A particularly precise flow forming is achieved according to an embodiment variant of the invention by advancing multiple compression rollers against the workpiece in an even distribution around the perimeter of the workpiece and with an axial offset relative to each other. Preferably, three or four compression rollers are arranged around the perimeter of the workpiece. In this way, the forming forces can be distributed over multiple compression rollers, allowing forming to take place in a manner that is particularly benign to the workpiece and the machine.

In the method according to the invention, the compression roller and the perimeter element of the spinning mandrel are axially displaced relative to the front element or the clamped workpiece in a coordinated manner. The compression roller and perimeter element in this case are preferably displaced differently, in particular if more complex internal contours of the rim well region are produced by means of a conically configured perimeter element.

In particular for producing a wheel with a drop-center rim, it is advantageous according to a method variant of the invention that, to form an axial undercut region in the rim, the at least one compression roller initially engages on a first diameter region of a conical perimeter element, next the at least one compression roller engages on a second diameter region of the perimeter element, which is smaller than the first diameter region, and then the at least one compression roller engages on a third diameter region of the perimeter element, which is larger than the second diameter region. The third diameter region here can have a diameter size like that of the first diameter region.

A drop-center region on the rim here can be arranged and formed as desired over the axial length of the rim. The drop-center region here can be configured not only in a central region but also on a side region of the rim which is opposite the radial hub region of the disc-shaped workpiece. In this way, a vehicle wheel is achieved with a rim having a drop-center region positioned relatively far outwards, which leads to a vehicle wheel that appears particularly voluminous. Vehicle wheels of this type with an outer drop-center region can be desirable for various wheel designs. With larger diameter regions of the conical perimeter element, the side surfaces of the drop-center region are formed and with a smaller diameter region the base of the drop-center region is formed under the action of the compression roller.

According to a further advantageous method variant of the invention, it is provided that a perimeter element is used, the axial length of which is smaller than the rim that is to be formed, and that wheels with different axial lengths of the rim are formed with the perimeter element. Thus, for instance with a substantially identical design of the disc-shaped hub region, different rim widths can be produced from a starting workpiece without major effort by the method according to the invention.

In principle, the forming can take place with an approximately horizontal axis of rotation. A particularly precise execution of the forming method according to the invention is achieved according to a method variant by setting the workpiece in rotation around a vertical axis of rotation during forming. The advancing of the compression rollers in this case takes place substantially in a radial, horizontal direction.

The invention is explained in more detail below with reference to preferred exemplary embodiments, which are illustrated schematically in the attached drawings. In the drawings, the figures show the following:

FIG. 1: a cross-sectional view of an essential part of a flow-forming machine according to the invention; and

FIG. 2: a cross-sectional view of a vehicle wheel produced according to the invention;

FIGS. 3a to 3c : cross-sectional views through a workpiece during various forming steps according to a variant of the invention;

FIGS. 4a to 4c : cross-sectional views through a workpiece in various forming steps according to a further variant of the invention;

FIGS. 5a to 5d : cross-sectional views through a workpiece in various forming steps according to a further variant of the invention;

FIGS. 6a to 6e : cross-sectional views through a workpiece in various forming steps according to a further variant of the invention.

A flow-forming machine 10 according to the invention has a spinning mandrel 20 and an opposite counter-mandrel 12, between which a workpiece 5 with a disc-shaped hub region 6 having a central centering hole and a perimeter region 7 that is to be shaped is axially clamped. The counter-mandrel 12 and the spinning mandrel 20 are each rotatably mounted by means of a drive flange 16 and 17 and are connected to a rotary drive (not illustrated), preferably each to a separate rotary drive, wherein the spinning mandrel 20, the counter-mandrel 12 and the clamped workpiece 5 can be driven in a rotary manner around a vertical, central axis of rotation 2 during forming.

The spinning mandrel 20 has a central main support 22, on the free end of which a ring- or disc-shaped front element 24 is releasably attached by means of screws. The front element 24, like the opposite counter-mandrel 12, which is provided with a forming surface 14, is adapted to the shape of the workpiece 5 that is to be clamped. In the event of a change of design of the workpiece 5, in particular of the hub region 6, the counter-mandrel 12 and the front element 24 can easily be released by means of the screw connections and replaced by appropriately adapted new elements. On the forming surface 14, a first rim flange 56 of a vehicle wheel 50 that is to be produced can be fashioned.

Furthermore, the spinning mandrel 20 has a sleeve-like perimeter element 30, which is mounted in an axially slideable manner on the main support 22. For the purpose of sliding, the perimeter element 30 is attached to a slide element 28, which is axially slideable by means of an adjusting cylinder (not illustrated) along the axis of rotation 2 between an extended starting position and a retracted end position, which is illustrated in FIG. 1. The perimeter element 30 has in its front or upper region an external conical surface 32, which tapers upwards. In a bottom end or central region, a forming region 34 is configured, which is designed for fashioning a second rim flange 58 on the vehicle wheel 50.

For forming the vehicle wheel 50 from the workpiece 5, multiple compression rollers 40, only one of which is indicated in diagrammatic form, are advanced against the perimeter region 7 of the workpiece 5 radially. The perimeter element 30 of the spinning mandrel 20 here is in the upper starting position, so that it acts as a counter bearing for the compression roller 40 engaging on the workpiece 5. The compression roller 40 is adjusted axially and to a certain extent also radially to form a rim region, wherein a wall thickness of the perimeter region 7 is thinned and rolled out to form the rim region. By means of a controller, as a function of the movement of the compression roller 40 the sleeve-like, conical perimeter element 30 is displaced axially, so that the desired internal diameter region is always provided at the desired position as a counter bearing for the compression roller 40. Depending on an intended length of the rim region, the perimeter element 30 remains stationary in an axial direction, so that during a further displacement of the compression roller 40 the material of the workpiece 5 is formed in the forming region 34 and thus the second rim flange 58 is flow-formed in the hub region 6, corresponding to the first rim flange 56.

In FIG. 1, to illustrate the flexibility of the flow-forming machine 10 according to the invention in wheel production, a total of three different lengths of the vehicle wheel 50 are indicated in diagrammatic form. The spinning mandrel 20 is thus to a large extent independent of the vehicle wheel 50 to be fashioned and can be employed for different axial lengths and internal contours. Only the electronic controller has to be adapted to the production without the need for any mechanical conversion work on the flow-forming machine 10.

In FIG. 2, in highly diagrammatic form, a further shape of a vehicle wheel 50 is shown, which can be produced according to the invention. The vehicle wheel 50 has a disc-shaped hub 52 and a drum-like rim 60, which are arranged in a substantially rotationally symmetrical manner relative to a wheel axis 51. In the region of the hub 52, a central hole 54 and further holes can be provided, depending on the design.

The rim 60 is provided with a rim well 62, which extends from a first rim flange 56 to a second rim flange 58. In a central section of the rim well 62, a drop-center region 64 is fashioned. The drop-center region 64 represents a radial narrowing in the rim well 62 and thus an undercut region 70, which is shown in diagrammatic form particularly clearly in FIG. 2. The drop-center region 64 can also have different dimensions and a different arrangement and can in particular be arranged closer to the freely projecting second rim flange 58.

The drop-center region 64 has two slightly oblique lateral flanks 66 running in a substantially radial direction, which extend as far as an approximately cylindrical base 68. The vehicle wheel 50 with the rim 60 and the drop-center region 64 can be produced by a method according to the invention with an appropriately conically configured perimeter element 30 as a counter bearing for externally engaging compression rollers 40. The perimeter element 30 in this case is axially displaced by means of a controller and appropriate adjusting element as a function of the position of the compression roller 40 to provide the appropriate diameter region.

According to the method variant of FIGS. 3a to 3c , a pot-shaped workpiece 5 with a radial hub region 6 and a drum-like perimeter region 7 is shaped by the method according to the invention into a flow-formed wheel blank according to FIG. 3b or into the finished wheel according to FIG. 3c , with an intermediate step, e.g. a wheel blank before turning, being illustrated in FIG. 3 b.

In the method variant according to FIGS. 4a to 4c a workpiece 5 is used, which is Y-shaped in a half cross-section and which has a radial hub region 6 and a drum-like perimeter region 7 extending to both sides of the radial hub region 6. In this method variant, a flow-forming machine can be used in which the counter-mandrel is configured identically or largely identically with the spinning mandrel and has a displaceable perimeter element.

In the method variant according to FIGS. 5a to 5d , a disc-shaped workpiece 5, also known as a round blank, is provided as the starting workpiece. This is shaped into an intermediate shape according to FIG. 5b by turning and partially splitting. The radial hub region 6 and a V-shaped perimeter region 7 are fashioned at this stage. The workpiece 5 is then finally shaped into the vehicle wheel 50 with a drop center via the intermediate step according to FIG. 5 c.

According to the further method variant of FIGS. 6a to 6e , a tubular workpiece 5, which forms the perimeter region 7, can be used as the starting workpiece. The workpiece 5 here can be clamped by a counter-mandrel, which is configured as a radial chuck, for instance as a four-jaw chuck. The spinning mandrel can thus be employed for processing the entire radial inside of the workpiece 5. According to FIG. 6e , a wheel 50 is achieved which consists only of the drum-like rim 60. Where a hub region is desired, this can be produced separately and attached to the rim 60 for instance by welding, in particular friction welding, or by screwing.

According to a further method variant, a tubular workpiece 5 according to FIG. 6a with flared regions on both sides can be held via a spinning mandrel according to the invention in a double-sided configuration and the drop center produced first by pressing or profiling, so that this region is used for axial holding or securing against axial sliding or for torque transmission for the subsequent flow-forming process with axial sliding of the sleeve-like perimeter elements. 

1. A flow-forming machine for producing a wheel, in particular a vehicle wheel, having a rim, from a workpiece, comprising a spinning mandrel, the outside of which is configured for forming the rim, a counter-mandrel, which can be displaced axially relative to the spinning mandrel, wherein the workpiece is clamped on the spinning mandrel and/or the counter-mandrel, a rotary drive for the rotational driving of spinning mandrel and counter-mandrel with the clamped workpiece and at least one compression roller, which can be advanced against the workpiece axially and radially for forming the rim, wherein the spinning mandrel has a sleeve-like perimeter element, which can be displaced axially to the workpiece during forming, the spinning mandrel has a main support, on which the perimeter element is mounted in an axially slideable manner, on a free front side of the main support a front element is arranged, wherein a radial hub or a drop center can be clamped axially between the spinning mandrel with the front element and the counter-mandrel, and a controller is provided, by means of which, while the rim is being formed, the at least one compression roller and the perimeter element of the spinning mandrel can be displaced axially relative to the workpiece in a coordinated manner.
 2. The flow-forming machine according to claim 1, wherein the sleeve-like perimeter element is configured in a conical shape at least in part, wherein the perimeter element tapers towards a free end.
 3. The flow-forming machine according to claim 1, wherein in a region of the perimeter element, a forming region is arranged, which is configured for forming a rim flange on the rim.
 4. The flow-forming machine according to claim 2, wherein for forming an axial undercut region on the rim the controller is configured for the relative axial displacement of the at least one compression roller and the perimeter element, so that the at least one compression roller initially engages on a first diameter region of the conical perimeter element, next engages on a second diameter region of the perimeter element, which is smaller than the first diameter region, and then engages on a third diameter region of the perimeter element, which is larger than the second diameter region.
 5. The flow-forming machine according to claim 3, wherein for the axial sliding of the perimeter element on the main support at least one adjusting element, in particular an adjusting cylinder or a spindle drive, is provided.
 6. The flow-forming machine according to claim 3, wherein the front element is fitted on the main support in such a way that it can be replaced.
 7. A forming method for producing a wheel, in particular a vehicle wheel, having a rim, from a workpiece, in which the workpiece is clamped on a spinning mandrel, the outside of which is configured for forming the rim, and/or a counter-mandrel, the clamped workpiece is set in rotation by a rotary drive and at least one compression roller is advanced against the rotating workpiece axially and radially, wherein the rim is formed, wherein the spinning mandrel has a sleeve-like perimeter element, which is displaced axially while the rim is being formed, the spinning mandrel has a main support, on which the perimeter element is slid axially, on a free front side of the main support a front element is arranged, wherein a radial hub or a drop center of the workpiece is axially clamped between the spinning mandrel with the front element and the counter-mandrel, and while the rim is being formed, the at least one compression roller and the perimeter element of the spinning mandrel are displaced axially relative to the workpiece in a coordinated manner.
 8. The forming method according to claim 7, wherein multiple compression rollers are advanced against the workpiece in an even distribution around the perimeter of the workpiece and with an axial offset relative to each other.
 9. The forming method according to claim 7, wherein while the rim is being formed, the at least one compression roller and the perimeter element are axially displaced differently.
 10. The forming method according to claim 7, wherein for forming an axial undercut region on the rim the at least one compression roller initially engages on a first diameter region of the conical perimeter element, next the at least one compression roller engages on a second diameter region of the perimeter element, which is smaller than the first diameter region, and then the at least one compression roller engages on a third diameter region of the perimeter element, which is larger than the second diameter region.
 11. The forming method according to claim 7, wherein a perimeter element is used, the axial length of which is smaller than the rim that is to be formed, and with the perimeter element, wheels with different axial lengths of the rim are formed.
 12. The forming method according to claim 7, wherein during forming the workpiece is set in rotation about a vertical axis of rotation. 